1. Field of the Invention
The present invention is directed to a dielectric heater, suitable particularly for an electronic cooking range, having a high efficiency of accommodating materials for heating as a system on the whole, the arrangement being such that an external configuration is formed to be flat, and a space for accommodating electronic appliances is considerably reduced as compared with a heating space in connection with the fact that an inverter system driving power supply is formed to be small.
The present invention further relates to a dielectric heater capable of preventing a remarkable decline in intensity of an interaction-space magnetic field of a magnetron whose dimension is orthogonal to a tubular axis of a frame-like yoke which serves as a draft air duct of cooling air, the decline being caused due to an increase in leakage magnetic fluxes leading from external surfaces of permanent magnets to an internal surface of the frame-like yoke.
2. Description of the Prior Art
A magnetron is typically cooled when being operated with being cooled. A conventional magnetron has such a structure that, as disclosed in, e.g., Japanese Utility Model Publication No. 54-35646, a yoke assuming a square in plan surrounds cooling fins closely fitted to an anode cylinder in a frame-like configuration, and the cooling air flows through an interior of the frame-like yoke while cooling the surfaces of the cooling fins. There arise, however, problems inherent in the conventional structure, such that (1) air passageways on both sides of the anode cylinder are narrowed when decreasing a lateral width in a ventilating direction with the result that the cooling process is effected with difficulty, and such that (2) after the cooling air has passed by the anode cylinder, the air does not immediately turn around the anode to the rear side of the anode cylinder, whereby there is not obtained a higher cooling efficiency than expected. For this reason, there is no choice but to increase the lateral width of the magnetron in the ventilating direction of the cooling air (ventilation flue).
On the other hand, a space for accommodating electronic components of an electronic cooking range exists so that its larger two sides are on the line of extension of a heating space. In the case of expanding a space for accommodating the materials for heating in the electronic cooking range, a length of one remaining side has to be reduced. It is required that the length of this remaining side be equal to or larger than a width of the air draft duct for the cooling air of the magnetron. When using a conventional magnetron driving power supply of such a system that a commercially available AC power supply is directly inputted to a step-up transformer for driving the magnetron, however, a large-sized transformer and also a large-sized oil-immersed capacitor are required, and these components have to be accommodated together with the magnetron in the electronic component accommodating space. As discussed above, when ensuring the large width of the ventilation flue of the magnetron, a capacity utilizing efficiency of the electronic component accommodating space is deteriorated. Besides, this space is large relative to the space for accommodating the materials for heating, resulting in deterioration in accommodation efficiency on the whole.
In recent years, an inverter power supply has been employed as a power supply for driving the magnetron. The inverter power supply contributes to considerable miniaturization of a transformer, inductors and capacitors. Owing to this inverter power supply, the electronic component accommodating space can remarkably be remarkably diminished as compared with the prior art magnetron driving power supply in which the commercially available AC power supply is inputted directly to the step-up transformer.
Even when making use of the foregoing inverter system driving power supply, however, it is, as explained earlier, required that the lateral width of the ventilation flue for the cooling air of the magnetron be large when being used in combination with the prior art magnetron. Consequently, there is created an additional problem in which the space for accommodating the electronic components of the electronic cooking range has to be much the same as that in the prior art.